Ischemic myocardium is vulnerable if revascularization cannot be achieved immediately. When one or more of the coronary arteries are blocked or otherwise unable to convey oxygenated blood to the heart muscles, tissue damage can occur in minutes.
Retroperfusion refers to a process where oxygenated blood is sent through the veins to irrigate and oxygenate the tissue in a direction opposite to normal blood flow. Coronary sinus retroperfusion techniques have been demonstrated to delay and/or reverse ischemic changes in the myocardial tissue, and may decrease infarct size and improve ventricular function following an infarction.
Pressure-controlled intermittent coronary sinus retroperfusion (PICSO) involves placing a device to periodically occlude the coronary sinus. When the device is inflated, venous blood draining into the coronary sinus is retained and passively redirected within the coronary venous system. While the mechanism is relatively simple, perfusing the myocardium with oxygen depleted venous blood may be less effective (additional oxygen is not being introduced to the tissue, and may also cause accumulation of toxic metabolites in the myocardium).
Synchronized retroperfusion (SRP) involves placement of a conduit catheter into the coronary sinus, and in synchrony with conduit inflation, oxygenated blood is pumped into the coronary venous system in a retrograde manner. Conduit inflation and blood injection into the coronary sinus occurs during diastole. The conduit is deflated during systole and blood flow into the coronary sinus ceases. SRP may involve use of complex pressure monitoring devices and pumps, and may require substantive setup, thus consuming precious time when re-establishing revascularization of the myocardium.
Simplified retroperfusion (SR) is similar to SRP, but does not include occlusion of the coronary sinus. Oxygenated blood is continuously injected into the coronary sinus with an infusion pump. While the tissue may be oxygenated, backflow into the right atrium instead of the coronary venous system may occur.